Crystal holder or setting



Aug. 15, 1933. P. EHLERT El Al. 1,922,032

CRYSTAL HOLDER 0R SETTING Filed March 1, 1929' 251 mm aka QM PatentedAug. 15, 1933 1 UNITED STA new CRYSTAL nowaa on SETTING Paul EhIertIand.losef l assler, Berlin, Germahy,

,assignors Drahtlcse to Telcfunlren Gesellschaft f iir Telegraphic m. b.H., Berlin, Qer

. imp. e'i' r i of wer Application 1; :1929, Serial 1%. 34am,

and in Germany March 2, 1925 4 Claims. ((1171-4271 r This inventionrelates to the piezoelectric art and deals more specifically with theproduction of a piezoelectric crystal holder.

It is known from the prior radio frequency art that crystals may be usedfor the purpose of keeping the frequency at a constant value and thatthese will allow to pass all oscillations being of the same frequency astheir natural period, while all other frequencies will be blocked.

Crystals of this kind, mostly of lamellar shape, have heretofore beenusually interposed between two plate-shaped electrodes, and it has beencustomary to accommodate them in a convenient boxed-shaped casingprovided with connecting terminals, say, pins, the space between theupper electrode and the cover of the casing being filled and packed withsome suitable soft substance, for instance, cotton, so as to preventloosening. Now, it has been found thatsuch crystal elements fail tofunction always in the same way, and it has been also found, moreparticularly speaking, that they are subject to variations of operationwhen their position is changed. For this reason, these crystal elementshave also been found rather unreliable when used in non-stationaryoutfits, for instance, on aircraft, automobiles and the like.

Now, the present invention is based upon the proper appreciation of thefact that the cause underlying the above trouble resides in that thecrystals are extremely sensitive in their oscillation performance to thepressure exerted thereon from the electrodes. As a matter of fact, experiments made along this line have demonstrated that the oscillationsof the crystals is dependent upon the pressure brought thereon asillustrated in Fig. 1. It will be noted from the graph that theperformance initially is gradually improved in proportion as thepressure grows until, ir. the presence of a certain optimum pressurevalue Po there is reached a more or less pronounced maximum or crest,but that the conditions are much impaired as the pressure is stillfurther increased, so much so that in the presence of a definitepressure P1 sudden failure to oscillate occurs. For this reason it is ofgreat practical importance to provide ways and means to adjust theoptimum pressure.

With this end in view, according to the invention. the crystal settingis so built that the electrodes are held together with the crystallamella by the agency of an adjustable spring pressure.

The manner in which the present invention is carried out will be morereadily understood from the following description taken in connectionwith the accompanying drawing in which:

Fig. 1 shows graphically the relation of the oscillation of the crystalto the varying pressures exerted thereon;

Fig. 2 is a sectional view taken on line 2-2 of Fig. 3 with the coverplate in place;

Fig. 3 is a plan view of the device with the cover plate removed; and

Fig. 4 is an exploded view of the device shown in Fig. 2.

Referring to the drawing, a is the crystal of 1 screw arranged on thecross piece 2. The assem-- bly is placed inside an insulating case Itwhich is closed at the top and at the bottom by means of cover plates hland 11.2, respectively. d1 and d2 denote plugs or pins which areconnected by cords with the corresponding electrodes bl and b2.

A crystal element of the kind here disclosed is readily adjustable tooptimum action; it can be used in any desired position, and can betransported without suffering any damage.

Having thus described our invention, what we claim is:

1. A piezo-electric crystal housing comprising an insulating body memberrecessed to form a receptacle, an electrode mounted in said body member,a contact member carried by said body and connected to said electrode, apiezo-electric crystal supported by said electrode. a second electrodemounted on said piezo-electric crystal, a second contact member carriedby said body and connected to said second named contact member, meansfor exerting pressure between said electrodes and said piezo-electriccrystal comprising a spring mounted to bear on said last named electrodeand means for adjusting the compression of said spring.

2. A piezo-electric crystal unit comprising an insulating body memberrecessed to form a receptacle, an electrode mounted in said body member,a contact member carried by said body and connected to said electrode, apiezo-electric crystal supported by said electrode, a second electrodemounted on said piezo-electric crystal, a second contact member carriedby said body and connected to said second named electrode member, andmeans for exerting pressure between said electrode members and saidpiezo-electric crystal comprising a support fixed to the open side ofsaid body member, a spiral compression spring mounted between said lastnamed electrode and said support, means for adjusting the compression ofsaid spring, comprising a screw in said support bearing on said spring,and a cover adapted to be fixed to the open side of said body,member,.

3. A piezo electriqcrysml unit comprising, aninsulating body memberrecessed to form a receptacle, an electrode mounted in said-member; apiezo-electric crystal mounted on said elec;. trode, a second electrodemounted on said piezoelectric crystal, a member fixed: to'isaid bodymember and spaced withrespectr to said last named electrode, aspirahsprini mounted between said member and saidl e1ect-tide, means,for adjusting the compression of said,sgring and, contact membersconnected with each of said electrodes.

4. A piezo-electric crystal unit comprising an insulating body memberrecessed to form.a;receptacle substantially open on two sides, a coveradapted to be fixed to one of the open sides of said body member, anelectrode for mounting in said body member adjacent to said cover, apieZo-electric crystal supported by said electrode, a second electrodemountedon said piezoelectric crystal, and means for exerting aipressurebetween said electrode members and said piezo-electric crystalcomprising a support fixed to, the other open side of said body member,a spiral compression spring mounted between said lastinamedfeleotrodeand said support, means for adjusting the compression of said springcomprising asci'pyr in said support bearing on said,sp ri ng-, a.co,yer. adapted to be fixed to said other open side Of, said body memberand means carried by said body member for connecting said eleetrodesinanele'etrical circuit.

P. EHLERT. J. FASSLER,

